Ore-furnace.



ORE FURNAQE- APPLICATION mm mmz's. I915.

Patented Dec. 14, 191

. in passing the a m it? il. l h. ill-if onu-runn'acn. I

original application filcdbctober 21, 1914, Serial No. 867,461.

Specification of Letters Patent.

Divided and this application filed March 25%1915. seri iuaiaeao.

To all whom it may concern:

Be it known that l, LEWIS E. Sumner, citizen of the United States, residing at Denver, Colorado, have invented certain new and useful Improvements in Ore-Furnaces, of which the following is a specilication.

The present invention relates to ore roasting furnaces and has for its object to provide an improved draft system whereby the annoyance of excessive temperatures in the middle litihrths will be eliminated.

The object of the invention is to provide an improved draft system for ore roasting furnaces of the general type comprising a cylindrical casing provided with a plurality of hearths or shelves formed therein and having a main hollow vertical shaft with rabble arms extending radially therefrom and adapted to rotate between the compartments formed by the several shelves or hearths.

A further object consists in ridding the roaster of as much heat as possible and get an advantage by putting it to subsequent useful purposes.

In former draft systems, it has been the general practice to havethe air enter at the bottom, pass upwardly through the furnace, and out at the top. In this arrangement as the air enters at the bottom, it is first heated up by the hot ore and then begins oxidizing sulfur and other constituents and various layers of ore the ac tual oxygen content is reduced and sulfur dioxid and other gases are formed.

Most sulfid ores, in roasting," will generate enough heat (if it could be conserved) to practically smelt themselves. In any event, there is an excess of heat generated in the middle hearths, the amount being greater than is desired for 'the'good of the apparatus. The practice has been to lessen the tonnage of ore put through and in consequence the draft of air to burn the ore when the central zone heat becomes greater than may safely be handled. This cuts down capacit ,The ore is fed at the to and is raked downward by the rabbling mechanism in a manner in general which is countercurrent to the travel of the gases.

It is apparent that the cold air admitted at the bottom must first become heated to a 5 critical ignition temperature before pracwliich desired as hot as possible.

tically any roasting will take place. The heat is furnished by the hot ore coming down, so that the air admitted actually cools the lower hearths as a result of this heat exchange. The cold ore at the top keeps the top hearths cool enough, but at the disad vantage of taking up heat from the gases 1 almost all the heat imparted to the gases at any stage of the roast could be sent out for subsequent beneficial. use, a better arrangement would be had than by trying to dissipate as much of the excess heat as possible from the central zones.

The subject matter of the present invention forms a divisional application from my co-pending application, Serial Number 867,461.

In the drawings the figure shows in vertical section a view of an ore roasting furnace having the present invention embodied tile are formed within the casing, being supllatented Dec. M, 1915,

ported from the inner circumference of the furnace casing and provided with a series of central superimposed openings 5 through which a cylindrical tile covering around the main hollow shaft extends. Any number of these shelves may be provided as required; in the present instance thefurnace is illustrated as having eight. Three of the lower shelves or hcarths are here shown as hollow and are of the well known type commonly referred to as muffled hearths. A plurality of openings 7 are formed in tho hearths or shelves at intervals around their central openings 5, while corresponding openings are formed in the alternate hearths at intervals around their circumferences.

By reason of the revolving rabble arms 9 carried upon the revolving shaft 6 and extending so as to move between the hearths or shelves, ore which is fed into the top of the furnace is kept constantly moving over the several hearths passing outwardly across rangements are provided for maintaining Varied drafts through the furnace.

According to the present invention two outlets 10 and 11 are provided at one side of the furnace, the former being on a plane with and opposite the topmost hearth, the latter being opposite a middle hearth. Each of these outlet or off-take pipes is provided with a damper 12 for regulating the amount of gas to be discharged therethrough. Intake openings 13 and 14. are provided for passing air into the furnace. These are arranged one opening into the lowermost hearth and one on a line with and opposite a middle hearth. They, too are similarly provided with dampers 15 and are each suitably connected with any source for furnishing oxidizing air to the ore. By this arrangement part of the air will pass from the middle hearth on up through and out of the discharge fine 10, while another part will be admitted through the lower intake fiue 14 and will pass out through the lower off-take flue ll.

The amount of the air supply and the manner in which it passes through the system can easily be controlled by suitable manipulation of the dampers 12 and 15 in the respective inletand outlet passages.

1n the foregoing description, the term cooling has been used in its literal sense, viz., removing the heat. Thus the heat is removed from the ore by the gases as a medium and since very hot gas is more useful than that which has had advantageous heat removed from it. The present draft system serves to withdraw these gases from the furnace in such manner that they may be subsequently made use of.

Since there is no necessity for all the air used by the ore on the various hearths to enter the bottom hearth and actually put out the ore by bringing its ten'iperature down below the temperature at which it will 1 keep on roasting, only a convenient p-rt is here adnutted. say one-third of the total amount. This passes up through the lower hearths, as shown, all becomes converted to a go d roaster gas, c. has a high sulfurous acid content and passes out at 11 as hot as is the temperature existing in this middle hearth. The reason this gas passes at the flue 11 instead of going up to the top outlet 10 by its natural draft chimney influence is because cold or ordinary atmosphere temperature air is blown in at 13 by a fan and 10 has a damper 12 which only allows a given amount of gas to pass out.

Since the amount admitted at 13 is usually in excess of the amount Withdrawn through 10, it is obvious that there is a back pressure on that part of the roaster from 10 to 11 and the excess at 13 will travel straight across the hearth to 11, and only that amount from down below 11 can escape through 11 which'corresponds to the amount of 11 opening, also regulated by a damper 12.

The result of all this is that there is a more uniform temperature throughout the various shelves of the roaster, the hot gas at the middle zone is removed with all its heat, air very much cooler than the gases sent through 11 is admitted to furnish the oxygen for roasting at the hearth where the ore has become hottest, so tending to chill it, and passes on up through the upper hearths where it meets the down coming ore, performing the necessary oxidation there, transferring its heat and passing out at 10.

It will be understooclthat the regulation of the air passing through the system controlled by these inlet and outlet passages is entirely independent from the air cooling system provided within the main hollow vertical shaft 6 and its rabble arms 9.

I claim as my invention: I

1. An ore roasting furnace comprising a cylindrical casing, a hollow vertical-shaft mounted therein, a series of ore floors surrounding said shaft, means for controlling the circulation of air through said furnace comprising a plurality,of air intake and gas outlet openings located at the bottom, top and middle parts of said casing, respectively, said inlet and outlet openings communicating through the outer furnace casing directly with the source of air supply and outlet lines, respectively.

2. An ore roasting furnace-comprising a cylindrical casing, a hollow, vertical, rotatable shaft mounted therein, a series of ore floors surroundin said shaft, air inlets near the bottom of said furnace, gas outlets near the top, and air inlets and gas outlets respectively, intermediate of the height of the furnace easing, each of said inlet and gas outlet openings being independently connected with the "source of air supply and outlet lines respectively through the outer furnace casing.

3. An ore roasting furnace comprising a, cylindrical casing, a plurality of superimposed ore floors therein, means for regulating the temperature on said floors comprising air inlets and gas outlets each provided with an adjustable damper, one or more of said inlets being located near the bottom of the furnace and one or more on a line with 1 an intermediate ore floor QI floors, one or more of said outlets being located at an intermediate ore floor or floors and one or more at the top of said casing, said air inlet and gas outlet openings being directly and inde pendently connected through the outer fur mice casing with the source of air supply and outlet fines respectively, whereby the circulation oiuir through different parts of the furnace can be controlled independently. 10

In testimony whereof, I {Il'llX my signature in presence of two witnesses.

'LEWIS BAILEY SKINNER. Witnesses:

T. R. ASHLEY,' R. B. HOSTER. 

